Constricted maxillary arch is often a significant dental and skeletal problem in field of orthodontics. Prior to the present invention, a fixed palatal expansion device generally consisted of a 4-band device with a midpalatal screw. In this example, the appliance had fixed bands on the maxillary first permanent molars and first premolars, connected on each side by a rigid bar, with both sides connected to each other by the screw. Such an appliance often consisted of 2 stabilizing bars, a screw with a hole in the middle for activation, and 2 metal blocks. These metal blocks are connected with each other by the screw and upon activation the blocks move apart from each other to achieve the transverse expansion of the upper jaw. In most instances, activation of the screw is performed by a pin shaped key. The appliance is initially cemented to the teeth and activated twice a day by the patient with the key until the desired expansion is achieved.
Looking at the above-described device from a clinical point of view, patients have a hard time finding the hole on the screw with the pin shaped key, inserting the key and turning the screw backwards in the direction of the throat by looking to an inverted image on a mirror. The hole on the screw is often very small; generally its diameter is less than a millimeter. Hence, even with the help of the pin shaped key, it is difficult to find. Furthermore, other risks exist. They include injuring the soft palate during insertion of the key and/or swallowing the key during activation. In some cases, accidental swallowing of orthodontic expansion appliance keys has been reported.
After the desired expansion is achieved, the activation of the screw is stopped and the appliance is maintained in the mouth for 3 months for stabilization and adaptation of the tissues. However during this time period, unwinding of the screw can happen thereby causing the blocks to retract, and some of the achieved expansion can be lost during the stabilization period.
Hence, a need exists for an effective palatal expander that is patient friendly. In particular, a need exists for a palatal expander that does not require a key, that is easy to use, and achieves the desired maxillary expansion without retraction of the device.